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Photosynthesis. Energy and Life. Energy is the ability to do work, and nearly everything you do requires energy, even while sleeping! Chemical energy is the energy stored in chemical bonds, and energy can change form.
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Energy and Life • Energy is the ability to do work, and nearly everything you do requires energy, even while sleeping! • Chemical energy is the energy stored in chemical bonds, and energy can change form. • The most important chemicals to provide energy is ATP (adenosine triphosphate) • ATP is made up of an adenine, ribose and a phosphate group.
Energy and Life cont. • Cells give off the energy stored in ATP by breaking its bonds. • ATP comes from food. • Heterotrophs must eat food to survive. • Autotrophs have the ability to make their own food. • They do this by the process of Photosynthesis.
Photosynthesis: An Overview • For photosynthesis to take place autotrophs must capture light energy from the sun. • Energy from the sun travels in the form of light, which we see as white light, but this is actually a mixture of different wavelengths that span the colors of the rainbow. • Plants gather the suns energy with light absorbing molecules called pigments. • Chlorophyll is the most common, however it does not absorb green light it reflects it!
Chloroplasts • Photosynthesis takes place inside the chloroplast. • These organelles hold many flat-bag shaped membranes called thylakoids, which are connected to one another and arranged in stacks. • These stacks are called grana. • Chlorophyll and other pigments are found there. • The liquid filled space around the thylakoids is known as the stroma.
High Energy Electrons • Light is a form of energy, and anything that absorbs light takes in energy. • When chlorophyll takes in light, much of that energy is moved directly to its electrons. • This is what makes photosynthesis work. • Plants use NADP to carry the electrons changing it to NADPH and carries the electrons to other parts of the cell.
Summary of Photosynthesis • In symbols • 6CO2 + 6H2O + Light = C6H12O6 + 6O2 • In words • Carbon dioxide + water + light = Glucose + Oxygen
Light Dependent Reactions • The first set of reactions in photosynthesis are the light Dependent reactions. • The light Dependent reactions take place in the Thylakoids. • Here TP and NADPH is made, and Oxygen is released.
Light Independent Reactions • In the light independent reactions plants use the ATP and NADPH made in the light dependent reactions to make high energy sugars. • During these reactions CO2 is taken from the air • These reactions take place in the stroma
The Process of Photosynthesis • Remember there are two sets of reactions in Photosynthesis. • The light dependent reactions and the light independent reactions. • The LDR take place in the thylakoids, these baglike membranes hold groups of chlorophyll and proteins are known as photosystems. • Photosystems take in sunlight and use it to add energy to electrons. • There are 2 Photosystems.
Photosystem 2 • The pigments of photosystem 2 absorb light energy and release high energy electrons. • These electrons get passed down the electron transport chain which is a group of carrier proteins • As light shines on the chlorophyll more and more electrons enter the electron transport chain. This happens when water molecules are broken down • This is when Oxygen is released.
Photosystem 1 • The electrons lose energy when they are pumped across the membrane. • Photosystem 1 light gives them energy again. • Then they go through the electron transport chain and make NADP into NADPH which is used in the next set of reactions.
SUMMARY of LDR • The light dependent reactions give off oxygen gas. • They also make ATP and NADPH. • These compounds are important for the cell. • They provide the energy needed to build sugars in the light independent reactions.
Light Independent Reactions: Making Sugars • ATP and NADPH store energy but are not stable. • During the LIR also called the Calvin Cycle, plants produce high energy sugars • These sugars are stable and can store energy for a long time. • One of the reactants in the Calvin Cycle is Carbon Dioxide, which comes from the air. • An enzyme joins CO2 molecules that are already in the cell producing energy rich Carbohydrates.
Sugar Production • With each turn of the cycle, a few carbohydrate molecules leave the cell which become the building blocks that plant cells use to make sugars, lipids, amino acids and other compounds. • The plant will use these compound to grow. • The rest of the high energy molecules stay in the cycle • Enzymes use ATP to change them to molecules that will join with the new CO2 Molecules and the cycle begins again.
Summary of LIR • The Calvin cycle uses compounds made in the LDR and CO2 from the air to make sugars. • The plant uses the sugars to meet its energy needs and to build molecules needed for growth. • When you eat plants you get that energy stored in the plants. • The end results from the LDR and the LIR is the energy in sunlight is is changed to chemical energy to be used by the plant.
Factors affecting Photosynthesis • Temperature: The higher the temperature the faster photosynthesis takes place. • Light: The more light or stronger the Light the faster the rate of Photosynthesis. • Water: The more water available the faster the rate of photosynthesis.
Photosynthesis in Extreme conditions • Plants lose water in their leaves through tiny openings that let in CO2. • When it is hot these openings are closed to help retain water, but by doing this less CO2 enters • Some plants have very special adaptations to deal with extreme conditions
C4 Plants • C4 plants have a special chemical pathway that gets carbon dioxide into the Calvin Cycle even when there is not a lot of CO2 Available. • This pathway uses extra ATP but allow plants to undergo photosynthesis when it is really Hot. • Corn and Sugar cane are examples of C4 Plants
CAM Plants • CAM plants save water by taking air into their leaves only at night. • In the dark CO2 is used to make acids. • During the day these acids are turned back to CO2 for photosynthesis. • Some examples of CAM plants are Pineapple Trees, and most desert Cactus.